These soldered-down storage chips use the PCIe interface and will feature 64-layer TLC NAND flash memory. They will be available in 128GB, 256GB, and 512GB capaciites, and offer read speeds of up to 1800MB/s and write speeds of up to 1200MB/s. The random 4k write IOPS is listed as 150k, which is the same as the chip's random 4k read IOPS.
While you can't upgrade or replace these chips, the main advantage is that they're a lot smaller than typical SSDs:
The SSD comes in a ball-grid array (BGA) form-factor which has been designed to further shrink the size of solid-state disks. BGA sized SSDs are about five times smaller than M.2 SSDs and hundred times smaller than a 2.5? drive. Not only do they integrate NAND flash memory, but also the controller, DRAM cache and everything else required for the SSD to function. For the computer and its software, BGA SSDs are drives with a PCIe interface or SATA interface.
Via: MyCE